Laser-induced thermal transfer processes are well-known in applications such as color proofing and lithography. Such laser-induced processes include, for example, dye sublimation, dye transfer, ablative material transfer, and melt transfer of fusible materials such as waxes. Such processes are described in, for example, Baldock, UK Patent 2,083,726; DeBoer, U.S. Pat. No. 4,942,141; Kellogg, U.S. Pat. No. 5,019,549; Evans, U.S. Pat. No. 4,948,776; Foley et al., U.S. Pat. No. 5,156,938; Ellis et al., U.S. Pat. No. 5,171,650; and Koshizuka et al., U.S. Pat. No. 4,643,917. The processes use a laserable assemblage comprising a donor element that contains the imageable component, i.e., the material to be transferred, and a receiver element. The donor element is imagewise exposed by a laser, usually an infrared laser, resulting in transfer of material to the receiver element. The exposure takes place only in a small, selected region of the donor at one time, so that the transfer can be built up one pixel at a time. Computer control produces transfer with high resolution and at high speed.
For the preparation of images for proofing applications, the imageable component is a colorant. For the preparation of lithographic printing plates, the imageable component is an oleophilic material which will receive and transfer ink in printing. In general, when an infrared laser is used, a separate infrared radiation absorber is also included.
While all of the above processes have been used, they each suffer from certain disadvantages. Dyes used in dye sublimation and dye transfer processes are frequently unstable over long periods of time. It is also difficult to obtain colored images of sufficient density. In addition, the range of colors available is limited. Ablative transfer processes often require high laser power densities in order to transfer sufficient amounts of the imageable component. While sufficient transfer density can be obtained using melt transfer of fusible materials, it is frequently undesirable to have waxes in the final image. It is also difficult to obtain the necessary resolution with these systems.